Abstract

The direct conversion of dc energy to RF pulses with high efficiency has many potential applications. They include: (1) the use of high-power electrical pulses for pulsed power devices and plasma-physics experiments; (2) various applications in high resolutions radar and time domain metro­logy; and (3) the generation of megawatt level microwave and millimeter-wave pulses. All of these experiments require the development of an appropriate switch or an array of switches which can switch high power with extremely fast risetime and zero jitter. For sequential waveform generation several methods have been tried [1,2]. In reference [1], a series of step recovery diodes was used; however only low voltage switching has been demonstrated. The prospects of extending this technique to a high power switch are poor because the step recovery diodes encounter breakdown problems at high voltage. In reference [2], a frozen wave generator was used for sequential waveform generation. A frozen wave generator consists of many segments of transmission line charged alternately with positive and negative voltage (Fig. 1). Two adjacent segments are joined by a silicon switch which can be closed with a laser pulse. To maintain a high conversion efficiency and a good waveform, it is essential that all the switches be closed simultaneously and rapidly. Jitter in the switching process produces random frequency modulation which removes energy from the fundamental frequency. Picosecond laser activated semiconductor switches seem ideal for this application. However, in reference [2], Proud, Jr. and Norman used a nitrogen laser which produced optical pulses with a time duration of a few nanoseconds. The advantage of the photoconductive switch was not fully utilized. In this work, we report the use of picosecond laser pulses for switching. A sequential waveform of two and one half cycles has been obtained with a voltage conversion efficiency of better than 95%.

© 1984 Optical Society of America